I wonder how 'smart' the PCM is on these...  Might be able to get away with fitting a resistor in the spare lambda plugs so the car thinks the lambdas are fitted. 

It may spot the lack of variation and flag a fault for that instead though.

if i use a fault code reader to turn the light off, sometimes it will come on within a few days, others it will stay off for up to 4-5, I have my mot soon, its a same, as the car runs fine, 

1 minute ago, steplce74 said:

if i use a fault code reader to turn the light off, sometimes it will come on within a few days, others it will stay off for up to 4-5, I have my mot soon, its a same, as the car runs fine, 

Just turn it off immediately before the MOT then.  

its just annoying seeing the light on, i have always had anything that needs doing to it repaired, and it has full service history, 85k miles, for a 1.6 ti-vct, it only does about 200 miles to a full tank but thats local driving with some motorway

i meant to add, i bought the car 4 years ago when the cat was replaced and this issue has only happened in the last few months

but been having lots of electric issues since i got it

I'm not really sure what you want us to suggest?  You've said the proper fix would cost £600-£1000 which probably isn't worth it on a car of this age.  I've offered a potential cheap bodge to keep the EML off (resistor in lambda plug) which may or may not work.

200 miles to a 50 litre tank sounds utterly horrific to me...I'd want rid of it immediately myself, wouldn't even contemplate spending £600 on a cat for it.

my engine light turned itself off and been off for 3 weeks now, 

That‘s good. Hope it doesn’t come back whilst driving to the mot test, that would be unlucky. 

On 10/9/2022 at 11:05 AM, steplce74 said:

it was put on before i got the car, trusted the car dealers, 4 years later it needs replacing, been quoted 600 for a  replacement but no warranty as it would be genuine otherwise over 1000 and i have no end of electric issues, the car runs well just has a engine light on

Tip never trust a car dealer salesman use a respectable mechanic to fit a correct part....u can knock mr trusty salesman down  few quid wen buying too rather than buy it nd 'trust' work be done

Firmly believe if you electrics are ok in car that replacing cat with correct cat, can be new or reconditioned/manufactured, or new OEM but must have those 4 sensors if your car has 4 plugs. Do that, plug it up to odb11 reader should be able to clear codes stored. Rerun engine till warm and if fixed no eml should return. If not fixed however, you got my problem. 

Could I get advice about replacing both bank 1 and 2 sensors. Current ones were bad old and dirty bad wires too. New sensors fitted both heated lambda and o2 so 4 wires each. Codes thrown for Hester control and bad connectivity for lambda and same for o2. 

After replacing these parts came from ebay but in genuine packaging and correct colours plugs etc Bosch for ford fiesta 06 1.6 petrol. 

Codes still coming up and for sum reason I cannot turn off eml. I use an autel code reader it usually can turn eml off. It needs mot asap. Could there mean ECU or pcm issue? I cant see any issues with the plugs n connecting wires.

an update, had another Lamba sensor fitted, engine light still on, an auto electrician came out and said a software update would cure it, the car drives fine and doesn't go into limp mode, if I turn the engine light on, after the 3rd start, it will come back on, the car only does short trips, the codes are PO156 and POO56, thanks

Did all wires been checked?

Made sure that it is the right sensor fitted for this model?

 

Car's performance is normal?

Any other error codes?

all wires checked, the right sensor was fitted, cars performance is fine, no other fault codes

It might really be a software malfunction.

The car's still have the stock catalyst?

Did you buy it as used or new?

not replacement cat 2 years ago, bought it used from a car dealer

I'm surprised you're still getting P0056.  That can really only be a wiring fault if you've had more than one post-cat sensor fitted on that side.

If it was just P0156 on its own then I'd say the cat is just worn out on that side.  But this is almost definitely wiring or PCM now.

As you've put up with it for 2 years, might as well just keep doing the same, clearing it for MOT.

46 minutes ago, TomsFocus said:

I'm surprised you're still getting P0056.  That can really only be a wiring fault if you've had more than one post-cat sensor fitted on that side.

If it was just P0156 on its own then I'd say the cat is just worn out on that side.  But this is almost definitely wiring or PCM now.

As you've put up with it for 2 years, might as well just keep doing the same, clearing it for MOT.

Could it be the catalyst?

12 hours ago, Bol said:

Could it be the catalyst?

If it was P0156 alone yes.  But P0056 isn't anything to do with the cat.

PCM then?

11 minutes ago, Bol said:

PCM then?

Wiring or PCM.  Can't diagnose any further than that over the internet.